C＃|逐字字符串字面量– @

在C＃中，使用特殊符号@创建逐字字符串。 @被称为逐字标识符。如果字符串包含@作为前缀，后跟双引号，则编译器将该字符串标识为逐字字符串，然后编译该字符串。 @符号的主要优点是告诉字符串构造函数忽略转义字符和换行符。 @符号主要有以下三种用法：

使用1：关键字作为标识符
该符号允许使用关键字作为标识符。 @符号是关键字的前缀，因此编译器将关键字作为标识符，没有任何错误，如以下示例所示：

例子：

// C# program to illustrate
// the use of @ by using keyword
// as an identifier
using System;
  
public class GFG {
  
    // Main method
    static public void Main()
    {
  
        // Creating and initializing the array
        // here 'for' keyword is used as 
        // an identifier by using @ symbol
        string[] @for = {"C#", "PHP", "Java", "Python"};
  
                // as and for keywords is 
                // as an identifier
                // using @ symbol
                foreach (string @as in @for)
                {
                    Console.WriteLine("Element of Array: {0}", @as);
                }
    }
}

输出：

Element of Array: C#
Element of Array: PHP
Element of Array: Java
Element of Array: Python

用途2：用于在字符串字面量打印转义序列，并在没有任何转义序列的字符串字面量使用换行符等。

如果将一个转义序列(如“ \\” (用于反斜杠)， “ \ u” (Unicode转义序列)， “ \ x” (十六进制转义序列)等)放置在字符串字面量而不使用@符号，则这些序列将由编译器自动解释。但是，“”(双引号)不是按字面意义解释的。它就像一个字符串插值。让我们看看带有@符号和不带有@符号的不同情况。

• 情况1：

  // taking a string literal and 
  // try to print double quotes
  string str1 = """";
  
  // printing output
  // this will give compile
  // time error as Unexpected 
  // symbol `' 
  Console.WriteLine(str1);
  

  在上面的程序中，双引号内的双引号作为字符串字面量被解释为单引号。

• 情况2：

  // taking a string literal prefixes
  // with @ and try to print double quotes
  string str1 = @"""";
  
  // printing output
  // this will output as "
  Console.WriteLine(str1);
  

  在上面的程序中，输出是双引号( “ )而不是”“

• 情况3：

  // taking a string in which we are storing 
  // some location of file but \Testing will 
  // interpreted as eascape sequence \T 
  // similarly \N
  string str1 = "\\C:\Testing\New\Target";
  
  // printing str1
  // this will give compile time error as
  // Unrecognized escape sequence `\T'
  // Unrecognized escape sequence `\N'
  // Unrecognized escape sequence `\T'
  Console.WriteLine(str1);
  

• 情况4：

  // taking a string and prefix literal with @ symbol. 
  // Storing some location of file 
  string str1 = @"\\C:\Testing\New\Target";
  
  // printing str1 will give output as 
  // \\C:\Testing\New\Target
  Console.WriteLine(str1);
  

程序：

// C# program to illustrate
// the use of @ in terms of 
// escape sequences and new 
// line and tab
using System;
  
public class GFG {
  
    // Main method
    static public void Main()
    {
  
        // If you use the below commented
        // the part then this will give
        // Unrecognized escape sequence error
        // string S1 = "\\welcome \to GeeksforGeeks \ portal \";
        // Console.WriteLine("String 1 is :{0}", S1);
  
        // By using @ in the given string 
        // it runs smoothly because
        // @ symbol tells the compiler to
        // ignore all escape sequences
        string S2 = @"\\welcome \to GeeksforGeeks \ portal \";
        Console.WriteLine("String 2 is: {0}", S2);
  
        // printing new line character in string literal
        // but it will make the string to break  
        // into a new line, see output
        string S3 = "This is \n C# non verbatim string";
        Console.WriteLine("String 3 is :{0}", S3);
  
        // By using @ symbol /n does not processed
        string S4 = @"This is \n C# verbatim string";
        Console.WriteLine("String 4 is :{0}", S4);
  
        // printing a string literal contains 
        // tabs and new line without using 
        // any escape sequence
        Console.WriteLine(@"Without Tab Sequence and New Line Character
                               C          C++      Java       Python");
    }
}

输出：

String 2 is: \\welcome \to GeeksforGeeks \ portal \
String 3 is :This is 
 C# non verbatim string
String 4 is :This is \n C# verbatim string
Without Tab Sequence and New Line Character
                               C          C++      Java       Python